Supported vanadium oxide-based catalysts for the oxidehydrogenation of propane under cyclic conditions

This short review documents some examples of the recent innovations in the field of catalytic selective oxidation aimed at improving process performance and process sustainability in general. Some strategies adopted in order to increase selectivity to the desired product are illustrated, including unconventional procedures for the oxidation reaction-the cyclic mode as compared to the cofeed mode-and special arrangements of the catalytic bed, as in the case of the oxidation of o-xylene to phthalic anhydride. The choice of which oxidant to use is also discussed, in relation to the process of oxidative desulphurization of gasoil.

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“…The same effect was not observed with catalysts in which vanadium oxide was deposited on alumina or titania [61][62][63] (Fig. 4).…”

Section: The Oxidized Pom Is Reduced By Methylnaphtholcontrasting

confidence: 44%

Catalysis for Society: Towards Improved Process Efficiency in Catalytic Selective Oxidations

2009

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“…Oxidative dehydrogenation (ODH) of propane to propylene represents an interesting alternative to the energy demanding dehydrogenation process and supported VOx demonstrated promising catalysts for this reaction [1][2][3][4][5][6][7][8][9][10]. Different supports have been tested, such as ZrO2 [11,12], TiO2 [13], V-substituted zeolites or silicalites [14], SiO2 [7,9,11] and Al2O3, usually as the -phase [3,[4][5][6]8,10,11,13].…”

Section: -Introductionmentioning

confidence: 99%

“…Different supports have been tested, such as ZrO2 [11,12], TiO2 [13], V-substituted zeolites or silicalites [14], SiO2 [7,9,11] and Al2O3, usually as the -phase [3,[4][5][6]8,10,11,13].…”

Section: -Introductionmentioning

confidence: 99%

EPR enlightening some aspects of propane ODH over VOx–SiO2 and VOx–Al2O3

Oliva

Cappelli

Rossetti

et al. 2009

Chemical Engineering Journal

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In the oxidative dehydrogenation (ODH) of propane to propylene VOx-based catalysts prepared by flame pyrolysis (FP) showed more selective than those prepared by impregnation. Furthermore, samples prepared by the same method were less active, but more selective when VOx was supported on SiO2 than on Al2O3. In order to assess V local structure, V 4+ ions showed useful labels to characterise these catalysts by EPR spectroscopy. Indeed, the spectrum of a (10 wt%V2O5) FP-prepared VOx/SiO2 catalyst was typical of isolated, tetragonally distorted, paramagnetic complexes of V 4+ forming a monolayer on the sample surface with a strong out-of-plane V 4+ -O bond. In a sample with identical composition, but prepared by impregnation, this bond showed a bit weaker.Furthermore, ferromagnetic domains of clustered V ions formed in the latter sample, hindering at least in part the accessibility to the catalytically active V-based centres. This gives evidence of the higher dispersion of V in the sample bulk provided by the FP preparation method with respect to conventional ones. A by far weaker V 4+ -O bond was revealed by the EPR spectrum of a (10%V2O5) VOx/Al2O3 sample, accounting for its higher oxygen availability, leading to higher activity, but lower selectivity. However, the same catalyst, when prepared by impregnation, showed a ferromagnetic resonance pattern so intense that no EPR spectrum was detectable at all and no information on the V 4+ -O bond strength was available in that case.Such semi-quantitative index of the V-O bond strength can be used as an index of oxygen availability, as a tool to assess catalytic activity and selectivity to the desired olefin.

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“…12 Vanadia supported on silica is found to be significantly more selective than that supported on alumina, which, in turn, is more selective than that supported on titania. [6][7][8]10 In an attempt to explain these observations, the contribution of support surface sites to the conversion of propane has been discussed. In particular, non-selective primary and secondary combustion reactions have been attributed to areas that are not covered by vanadia species.…”

Section: Introductionmentioning

confidence: 99%

Topology of silica supported vanadium–titanium oxide catalysts for oxidative dehydrogenation of propane

Hamilton

Wolfram

Müller

et al. 2012

Catal. Sci. Technol.

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Two-dimensional vanadia and titania surface clusters were hosted on the walls of the hierarchical pore system of mesoporous silica SBA-15. The topology of the catalyst surface was varied by sequential grafting of vanadium and titanium alkoxides generating an extended library of mixed (VO x ) n -(TiO x ) n /SBA-15 catalysts. The surface of the catalysts was analyzed by FTIR, UV-vis, Raman, and NEXAFS spectroscopy. Electron microscopy, X-ray fluorescence, X-ray diffraction, and nitrogen adsorption have been applied to characterize chemical composition, micro-and meso-structure of the materials. Segregation of nano-crystalline vanadia and titania particles was excluded by UV-vis, Raman and NEXAFS spectroscopy. Monolayer coverage of titanium oxide surface species has been achieved in the range between 17 and 19 wt% Ti loading corresponding to 6-8 Ti atoms per nm cat 2 and Si/Ti ratios between 3.3 and 2.8. Up to a critical total metal loading, vanadia is grafted on both the silica surface and surface titania species yielding tetrahedrally coordinated vanadium oxo-species characterized by low nuclearity and moderate catalytic activity. A volcano-type dependency with respect to the propylene space-time yield has been observed in the oxidative dehydrogenation of propane. The maximum in productivity of propylene is attributed to a particular surface topology that is characterized by (VO x ) n islands embedded in a matrix of dispersed titania species forming an almost complete combined vanadia-titania monolayer on the silica surface.

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Supported vanadium oxide-based catalysts for the oxidehydrogenation of propane under cyclic conditions

Cited by 50 publications

References 13 publications

Catalysis for Society: Towards Improved Process Efficiency in Catalytic Selective Oxidations

Catalysis for Society: Towards Improved Process Efficiency in Catalytic Selective Oxidations

EPR enlightening some aspects of propane ODH over VOx–SiO2 and VOx–Al2O3

Topology of silica supported vanadium–titanium oxide catalysts for oxidative dehydrogenation of propane

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